Categories
Coffee review Coffee Roasters Observations Science history slow

Waiting for a green light at Alchemy, St Pauls

8 Ludgate Broadway, St Pauls
Alchemy Coffee

Alchemy, “a seemingly magical process of transformation, creation or combination”, is certainly a cafe that lives up to the dictionary definition of its name. The branch, on Ludgate Broadway near St Pauls, is the outlet that ‘showcases’ the coffee of Alchemy Roasters. On walking into this cafe, I was presented with a menu of two types of beans for espresso based drinks or two different beans for filter/aeropress. Both sets of coffees came with tasting notes. After a brief chat with the friendly barista I went for the San Sebastian with aeropress. Notes about the origins of the coffee are dotted around this superbly sited cafe (its location is ideal for people watching). The coffee is directly traded (where possible) and, if lattes or cappuccinos are your thing, there are also details about the farm that produces the milk.

Although there were cakes on the counter, I had just had lunch and so had to pass on what looked to be a good selection of edibles. The coffee though was certainly very good and definitely an experience to be savoured. As, perhaps I should have expected, when the coffee arrived it came in a beaker reminiscent of chemistry laboratories. From my chair in the corner, I could watch the preparation of the coffee behind the counter, the people coming into the shop to order their coffee and the crowds passing by outside.

E=mc2 Einstein relativity in a cafe
Scales at Alchemy. Weights on one side, chocolate on the other, it can only mean one thing: energy-mass equivalence

Close to where I was sitting was an old style set of measuring scales. This see-saw balance had weights on one side and chocolate on the other. Perhaps this connection seems tenuous, but for me weights on one side of the scales and an energy bar (chocolate) on the other side could only mean one thing:

E=mc²

The equation relating energy and mass for a particle at rest derived, and made famous by Einstein. The equation comes from Einstein’s theory of special relativity which states that nothing can be accelerated to faster than the speed of light (in a vacuum). First set down in 1905, the theory has some very odd predictions, among which the best known is probably the twin paradox (details here). The idea is that a moving clock will be observed to run slowly by a stationary observer, a prediction that has been confirmed several times by experiments using atomic clocks (here).

San Sebastian via Aeropress
Coffee is served at Alchemy

Moreover, the equation states that mass and energy are equivalent and that a small amount of mass can produce an awful lot of energy, (details here). A detail which will bring this story of a cafe-physics review nicely back to the Alchemy cafe, to London and to the importance of slowing down. The connection is through a set of traffic lights in Bloomsbury. Back in 1933, Leo Szilard was waiting to cross the road at the traffic lights at the intersection of Russell Square with Southampton Row. Szilard had recently escaped from Nazi Germany and was spending his time as a refugee in London pondering different aspects of physics†. That September day, Szilard was thinking about a newspaper article featuring Ernest Rutherford that he had read earlier. In 1901  Ernest Rutherford, together with Frederick Soddy, had discovered that radioactive thorium decayed into radium. The changing of one element into another could be considered a type of modern day alchemy. However Rutherford did not believe that there could ever be a way of harnessing this nuclear energy. In the article read by Szilard in The Times, Rutherford had dismissed any such ideas as “moonshine”. Szilard was forced to pause his walk as he waited for the traffic lights to change. Those few moments of pause must have helped clear Szilard’s mind because as the light went green and Szilard was able to cross the road, a thought hit him: If every neutron hitting an element released two neutrons (as one element was transmuted into another), a chain reaction could be started. As part of the mass of the decaying atom was released as energy, it would mean that, feasibly, we could harness vast amounts of energy; E=mc².

This idea, a consequence of spending five minutes waiting for a traffic light rather than checking Twitter (not yet invented in 1933), proved to underpin both the nuclear fission which we use in electricity generation and the nuclear fission that we’ve used to develop weaponry. It makes me wonder what alchemy we could conjure in our minds if we stopped to enjoy the transformations of the coffee beans at Alchemy.

 

Alchemy (cafe) is at 8 Ludgate Broadway, EC4V 6DU

† A book that some may find entertaining is:

“Hitler’s Scientists”, John Cornwell, Penguin Group publishers, 2003. The book contains this anecdote about Szilard: As Szilard was of Hungarian-Jewish descent, he fled Germany to Britain via Austria on a train a few days after the Reichstag fire of 1933. On the day he left, the train was empty. One day later, the same train was overcrowded and the people leaving Germany were stopped at the border and interrogated.  An event that prompted him, a few years later, to reflect “This just goes to show that if you want to succeed in this world you don’t have to be much cleverer than other people, you just have to be one day earlier than most people.” Something to reflect on in today’s refugee crisis perhaps.

Categories
Coffee review Coffee Roasters General Observations slow

Time for a slow coffee?

enamel mug, teh halia, Straits Times kopitiam
This enamel mug connected glass to the Giants Causeway (Straits Times kopitiam)

Every two weeks, the Daily Grind on Bean Thinking is devoted to what I have called a cafe-physics review. The point of these reviews is to visit a café, slow down and notice what has been going on in a cafe physics-wise. I focus on physics because it is my ‘specialist’ area but the point is to notice the connections between the coffee, or the cafe and the world around us. To see how what is going on in your mug is reflected in the science of the wider universe. Realising that things that seem disparate are in fact connected: It is the same maths that describes electrons moving in a metal and the vibrations on the surface of a cup of coffee. That sort of connection to me is mind boggling. Yet there is more. Thinking about the connections between physics and coffee can lead to meditations on the environment and sustainability, or considerations about how our attitude to drinking coffee changes our perception of it.

Everything is connected.

Parquet floor at Coffee Affair
How many people have walked on this floor? The story of evolution at Coffee Affair

It is my strong belief that whenever we go into a cafe, order a coffee and then proceed to sit down with our smart phones or tablets and check our e-mail or our Twitter accounts we lose a fantastic opportunity. It is the opportunity to be properly present and to notice what is going on around us. It is the opportunity to slow down and to appreciate what life has given us and the surprising things that the world has to offer. To look at the beauty and the complexity of the world and to say ‘wow’.

This appreciation is open to us all, provided we seize the opportunity to slow down and take that time to enjoy our coffee.

So, this week’s Daily Grind is an invitation. It is an invitation open to anyone who sits down with a coffee. If you notice anything peculiar, or interesting, that you feel deserves a mention as a cafe-physics review why not write an edition of the Daily Grind? It does not matter where in the world you are or what your level of science knowledge is. If a full Daily Grind article is too much but you have a great observation, write a paragraph review of your favourite cafe and I’ll add it to the cafe-physics review map. Think that you don’t know enough science? Never mind, share your idea with me and we can work on it together.

Hasten coffee, long black, black coffee, espresso base
Sometimes the link with physics/science is a little bit tenuous, as it was at Espresso Base

Your observations need not be physics-based. It would be great if it is based on some aspect of science, but, as past examples have shown, this link can be a little tenuous if the cafe/subject warrants it.

So, over to you. I hope that someone will respond to this invitation. Please do contact me if you would like to pen a review or if you have any questions. It is my hope that you are all enjoying such great coffee in the huge variety of cafe’s that we now have that there will be plenty of opportunities for people to slow down and to notice and then to share it with the Daily Grind.

Please contact me here, or in the comments section below. I look forward to hearing from you.

 

Some brief guidelines for a cafe-physics review:

1) The cafe should, preferably, be a good independent.

2) Any science/history etc. needs to be verifiable but, as mentioned, if you’ve noticed something great but are unsure of the science, get in touch and we’ll work something out together.

3) If you have noticed something fascinating with your coffee but at home and not in a café, contact me anyway.

4) Please do not write a cafe-physics review of any cafe you are financially associated with. I will have to refuse/delete any ‘reviews’ that I find are adverts.

Categories
Coffee cup science General Observations slow Tea

What haloes and crowns reveal about your coffee

Coffee Corona
Look carefully around the reflected white light. Do you see the rainbow like pattern?

Several weeks ago I had been enjoying some very good black coffee at OJO in Bangsar, KL. As is fairly typical for me, I had been trying to observe the white mists that form just above the coffee. White mists are fascinating, tissue-like clouds that you can often see hovering above the coffee. They form, tear suddenly and then reform into a slightly different pattern. As I was photographing my coffee, I noticed what seemed to be interference patterns on the mists (see picture), just like oil on water, a rainbow-like shimmering over the coffee surface. Yet that explanation did not make sense; interference patterns form because the layer of oil on water has approximately the same thickness as the wavelength of visible light (see more info here). The water droplets that make up the white mists are a good 15 times thicker than the wavelength of light. It is not possible that these mists are producing interference effects, it has to be something else.

Then, last week and back in London, I was walking towards the setting Sun one evening when I saw what looked like a rainbow in a cloud. What caused this and how was it related to what I had seen earlier in my coffee? A short trip to the library later and it was confirmed. What I had seen in the clouds was most likely a Sun-dog. Formed by the refraction of sunlight by ice crystals in the atmosphere, Sun-dogs manifest as bright regions of rainbow. The Sun-dog appeared in cirrus clouds because these are made from the sort of ice crystals that produce brilliant Sun-dogs. These ice crystals are flat and hexagonal so they refract sunlight exactly as does a prism. Just like a prism, red light and blue light will be refracted by differing amounts and so they will appear at different places in the sky. The minimum angle of refraction produces the most intense colouration and, for hexagonal platelets of ice, this occurs at 22º away from the light source.

Sun-dog, Sun dog
A Sun-dog in the clouds to the right of the setting Sun

I do not find degrees a particularly helpful way of thinking about distance but what helped me is that, in terms of the sky, if you hold your outstretched hand out at arms length, the distance from your thumb to the tip of your finger is, approximately, 22º. Hence, if you see a halo around the Sun at about that distance, it is most likely a refraction effect due to ice crystals in the sky and if you see an intense rainbow roughly parallel to the elevation of the Sun, it is very likely to be a Sun-dog.

What does this tell us about the colours in the mists above the coffee? Well, clearly the mists are not made of ice crystals but neither is the ‘rainbow’ colouring as far as 22º from the light source (a light bulb reflected in the coffee). Also, the rainbow is less vivid and, if you look closely, inverted from the rainbow in the clouds. In the cloud, the inner edge of the arc was red and the outer edge blue, in the coffee, the outer edge is more reddish, while the inner is more blue-ish. This is another clue. On the same evening as I had seen the Sun-dog, there was a full moon and around the Moon was a glowing ring, tinged slightly reddish on the outside. The ring was far closer to the Moon than the Sun-dog had been to the Sun. This Moon-ring, and the coffee colouring are the same effect, they are examples of ‘corona’ (literally crown) and they are caused by diffraction of light rather than refraction.

straw, water, glass
It is refraction that makes the straw appear broken in this glass of water.

Refraction we are all quite familiar with, it is the bending of a straw in a glass of water as you look through the glass. Diffraction is a little more tricky, but it is a consequence of how the light moves past an object. It can be understood by thinking about how water waves pass objects in a stream (or by playing with the simulation here). The amount that the wave is diffracted depends on both the size of the object and the wavelength of the wave. As blue light has a much shorter wavelength than red light, the blue will be diffracted by a different amount to the red. If the objects diffracting the light are of a similar size (as water droplets in white mists are going to be) a spectrum, or a rainbow of colour will appear around the light source. The more uniform the droplet size, the more vivid the spectrum in the corona. The thin cloud around the Moon that evening was made up of many different sized droplets and so the rainbow effect was very subtle. In contrast, around the reflection of the light bulb in the coffee, the water droplets in the white mist are a fairly similar size and so the spectrum is more vividly seen.

Seeing rainbow effects in the sky (or in the coffee) therefore gives us many clues as to what is in the sky or indeed, levitating above the coffee. Please do send me any pictures you have of coronae around light source reflections in your coffee, or indeed sun dogs if you are fortunate enough to see them*.

* Sun dogs are in fact apparently fairly common, it is more that we have to be attentive to see them.

Categories
Coffee review Observations Science history slow Sustainability/environmental

In the Greenhouse at CoffeeGeek

Coffee Geek and Friends, Coffee Victoria
Coffee Geek and Friends

Earlier this year, a new café opened up in Victoria. Coffee Geek and Friends is located at the far end of Cardinal Place as you enter from Victoria Street. Cardinal Place is an odd sort of shopping centre, a small collection of shops with a glass roof. The building site near Coffee Geek as well as the constant stream of people rushing to and fro make Coffee Geek an ideal place to spend some time watching the world go by. Coffee is by Allpress espresso and is served in very individual mugs. Apparently there is a range of geek-ery in the cafe including a ‘centre piece’ water filter but I admit I missed that as I was too focussed on my coffee. Coffee Geek and Friends is definitely a cafe to keep in mind (along with Irish & June’s) if you need a good place to meet near Victoria Station.

It was a very humid day when I enjoyed my coffee at Coffee Geek and, because the mug had not been pre-warmed before my Americano/long black (my notes don’t specify which) was poured into it, condensation quickly formed around the rim of the mug. The condensation forms for the same reason that dew forms after a cool night: the vapour pressure of the water above the coffee (or the ground) has reached the dew point at the temperature of the mug. The lower the temperature, the lower the vapour pressure has to be for the water in the atmosphere to start condensing into liquid droplets. Hence you will often find that your coffee is more ‘steamy’ on a winter’s, rather than a summer’s day.

Condensation on mug in CGaF
Look carefully at the rim of the mug. Do you see the condensation?

Just over two hundred years ago, William Charles Wells made a study of dew. He observed the weather conditions under which dew formed. He observed on which surfaces dew collected. He noted whether the dew formed on space facing surfaces or ground facing surfaces. After several years of careful study he published his “Essay on Dew” in 1814. His work, showed that the earth radiated heat at night (when it was not being kept warm by the Sun) and therefore that space was cold. Cloud cover reduced the amount by which the ground cooled which implied that cloud cover was acting as a type of blanket for the Earth, keeping the heat trapped inside. Later calculations of the balance between the heat radiated by the Earth and the heat received by the Sun confirmed that, without some heat getting trapped by clouds and ‘greenhouse’ gases in the atmosphere, the earth would be a good 30 C cooler than it is observed to be. Although these calculations are just rough, “back of the envelope” figures, detailed calculations confirm that the Earth is in a delicate balance, heated by the Sun, cooled by radiation and kept warm (and live-able) by a layer of natural greenhouse gases. This “natural greenhouse effect” has been necessary for our development, the problem is that now we are adding yet more greenhouse gases to the atmosphere which threatens to tip the established delicate balance by a few degrees.

Cardinal Place roof, greenhouse
The roof of Cardinal Place shopping centre. A very appropriate place for a meditation on the greenhouse effect

What we now call the greenhouse effect are these extra gases, which are more efficient at trapping heat within our atmosphere. If you can imagine what has been happening over the past three hundred years or so as we have been pumping yet more of these gases into the atmosphere at an accelerated rate, we are in danger of tipping this delicate balance towards further heating of the earth. The 2015 Paris Climate Conference is being held with the aim of requiring all nations to agree to a legally binding commitment to reduce the amount of extra greenhouse gases that we emit to a level that will only result in a temperature increase of 2C. To achieve this requires all of us to work together to reduce our own ‘carbon footprint’. Each of us will have to find our own, individual ways to reduce our emissions but perhaps when we look at the condensation on the rim of our coffee cup, we could remember William Charles Wells and his essay on dew and just think, what can I do, at this moment, to reduce my carbon footprint? Maybe it could be something as simple as turning off that phone (to conserve the battery) and watching what is going on in a café instead. A small gesture but one that would be good for us as well as the earth.

Coffee Geek and Friends is at the northern end of Cardinal Place shopping centre (opposite Westminster Cathedral).

As a Coffee Geek note, I would like to just comment that my notes on Coffee Geek and Friends were written using a “linux-sure” ball point pen. Not particularly environmentally friendly but definitely quite geeky.

Categories
General Home experiments Observations slow Sustainability/environmental

An opportunity to become a cafe-scientist

coffee, Timberyard, wooden tray
A great place to sit and do some citizen science: Timberyard, Seven Dials has plenty of seats outside.

There are many things to be gained from putting down your smart phone when you enter a café. Firstly, there is the opportunity to fully experience the coffee. The sounds as it is made, the smell, the taste, even the feel of the coffee. Then there is the opportunity for people watching; their behaviour as they order their coffees or have their meetings or try to alleviate boredom while playing with their smartphones. Of course, there is also the opportunity to look at the history of the café and its surroundings, to think about a café-physics review or just slow down and notice things. There’s always something interesting going on.

If you are lucky enough though to be in Athens, Barcelona, Belgrade, Berlin, Copenhagen, London, Manchester, Milan or Rome there is now even more reason to put down that phone while you savour your coffee. By doing so, you could be helping scientists with a few questions that they have about atmospheric pollutants. If you are not in one of those cities, you miss out this time, but you may want to keep reading because if enough people get involved now, perhaps next time the iSPEX-EU project may come near you.

contrail, sunset
What sort of aerosols and pollutants are floating in the atmosphere above your head at this moment?

The question is, what are the atmospheric pollutants that are in the air near where you are now? Perhaps you are in a café on a main road and the answer seems obvious, it is those cars and buses that keep passing by. But there are in fact many forms of atmospheric aerosols or particles and they range in size from a few nanometers to tens of microns (which, in terms of coffee grind is from much smaller than the smallest Turkish coffee to approximately the size of a small particle in an espresso grind). Is it really so clear that where you are, in the centre of that big city, is that polluted? If on the other hand you are on the coast in Barcelona, just how salty is that salty sea air? The iSPEX-EU project allows you to measure it and find out.

These particles of dust, salt and soot etc. can have  an effect on human and animal health, so clearly we want to know more about their distribution and their prevalence. But there are also, more subtle reasons why we may want to know about them. They may have an effect on global warming and they are certainly needed in order for clouds to form, (though as yet we still do not fully understand this process). We need more data about what aerosols are around and where they are to start to know what questions to ask (let alone answer) about health, the climate and cloud formation. Yes, we have satellite measurements and pollution data at specific locations, but what people are missing is that local information. What are you actually breathing? When you look up at the blue sky, what pollutants (or other type of aerosol) are you looking through? Can we get enough data to know how the air quality varies between the cafés of Hackney and those of Hammersmith?

Skylark Wandsworth
Another ideal cafe for iSPEX-EU measurements, great coffee and a lovely outdoor seating area at Skylark cafe, Wandsworth Common

To get this data the scientists involved in iSPEX-EU need people, many people. People who are willing to spend 5 minutes turning their iPhone (sadly it is an iPhone-only project) into a pollution detector. The more people that they can get measuring, the more data that they will be able to obtain. All you need is an app from the App-store and a (free) device that fits over your iPhone camera which you can pick up from somewhere local to you. Then, you just take a seat outside the café on a lovely blue sky day between now and the 15th October, aim your phone at the sky and take a series of photographs which are shared back with the scientists coordinating the project. If you are curious to know how your air quality compares with that in another participating city, you can check the live map to see how the measurements are going across Europe.

The device works by looking at the colour spectrum as well as the polarisation of the light reaching the camera as a function of angle. This information gives tell-tale clues as to the size of the aerosols as well as their prevalence. There is a lot more information on the website of the iSPEX-EU project and so I would recommend that if you do want to know more, you click their link here. In the meantime, why not sign up with iSPEX-EU, take a seat outside in that café and enjoy a great coffee knowing that, as you do so, you are contributing to our understanding of atmospheric science.

If you do decide to participate, please let me know of any great locations that you find, both for the coffee and the measurements, or share your pollution measurements with me in the comments section. I look forward to seeing some great data on the live map.

To get involved with the iSPEX project, you can follow the link here.

 

Categories
General Observations Science history slow

Seeing things at a kopitiam (coffee shop)

Rocky, Bangsar, KL, Malaysia, koptiam
A kopitiam in Bangsar, Kuala Lumpur, Malaysia

One of the great things about travelling is exploring the different cafe and coffee cultures in different countries. Is it the coffee that is important? Or food, alcohol or maybe just the opportunity for socialising? In Singapore and Malaysia, the “kopitiam” (or coffee shop) is a familiar part of each neighbourhood. Each kopitiam serves local coffee (kopi) and a variety of foods which are usually prepared while you wait, from stalls around the edge of the kopitiam. The kopitiam provides a space for socialisation and meeting people over a bowl of steaming noodles. Inside electric fans are blowing continuously in an effort to lessen the heat. Frankly, the local coffee is not to my taste but there are plenty of other things to eat and drink in each kopitiam. A breakfast of “kueh” and black tea for example is a welcome change from toast at home! In many areas of Singapore, and to a lesser extent Malaysia, local kopitiams are closing to make way for the new style cafés which serve a range of freshly roasted, pour over or espresso based coffee. Not being Malaysian or Singaporean I do not want to comment too much on that, I guess it is similar to the decline of the “caffs” in the UK. Mourned by many in the community but welcomed by others for the improved quality of the coffee.

straw, water, glass
An everyday example of refraction. The water refracts the light to make the straw appear ‘broken’.

However, with so much going on in a kopitiam, the temptation to look at a kopitiam-physics review was too great, especially when I started to “see things” at the edge of the shop. Am I going mad? No, it was not that my imagination was playing with my mind; I saw the ingredients for a mirage. You see, at the edge of the kopitiam the hawkers will cook noodles, or rice dishes etc. and this creates heat. Above some stalls there will be clouds of steam rising as the noodles boil in a pan. The clouds appear white because of the scattering of light by reasonably sized water droplets (more info here and here). Above other stalls, there is no steam but the heat created by the cooking makes the air immediately above the stove warmer (and therefore less dense). This less dense air refracts light less than air at room temperature. It is refraction that causes that straw in your iced coffee to look as if it is broken as you look at it (see picture). In the kopitiam, it means that as you look through this region of warm air you see a wobbly or wavy type pattern as the light from outside is refracted by different amounts depending on the temperature of the air that it goes through. It is this that is the primary ingredient for seeing a mirage.

The fact that air at different temperatures refracts light by different amounts is the reason for mirages in the desert. Frequently, warm air is trapped at ground level by a layer of cold air above it. The light is bent as it travels through these layers (see diagram here) and so it may appear as if they sky is on the ground (which the brain will interpret as a pool of water on the ground). Conversely, if there is a layer of cold air trapped beneath a layer of warm air, the light is bent downwards and so objects that are usually below the horizon due to the curvature of the earth can be seen (illustrated by the diagram here).

Edmond Halley, Canary Wharf, Isle of Dogs, view from Greenwich
The view towards the Isle of Dogs (and Canary Wharf) from Greenwich. Things have changed a little since Halley’s time.

Back in 1694 Edmond Halley (who drank coffee with Isaac Newton at the Grecian) was investigating the evaporation of water as a function of temperature. He wanted to see if evaporation alone could explain the rainfall and the quantity of water in the river system. As he did so he noticed that, in still air, there was a layer of water vapour that formed above the bowl of evaporating water. He noticed this because it refracted the light in an unusual manner. At the time, there was reported to be an unusual phenomenon that occurred at high tide near Greenwich. It seems that cows used to graze on the Isle of Dogs in London. Ordinarily the cows could not be seen from Greenwich because they were too far away, but occasionally, at high tide, the cows would be visible. Putting together what he knew about the evaporating water Halley wrote “This fleece of vapour in still weather… may give a tolerable Account of what I have heard of seeing the Cattle at High-water-time in the Isle of Dogs from Greenwich, when none are to be seen at low-water (which some have endeavoured to explain by supposing the Isle of Dogs to have been lifted by the Tide coming under it.) But the evaporous effluvia of water, having a greater degree of refraction than the Common Air, may suffice to bring these Beams down to the Eye, which when the Water is retired, and the vapours subsided with it, pass above, and consequently the Objects seen at the one time, may be conceived to disappear at the other”*. I think that although he had the mechanism correct (in terms of refraction), the cause of this odd refraction was temperature inversion and a layer of cold air immediately above the Thames rather than water vapour but what do you think? Let me know in the comments section below.

 

* Punctuation and capitalisation kept as in original. Taken from Edmond Halley, “An Account of the Evaporation of Water, as It Was Experimented in Gresham Colledge [sic] in the Year 1693. With Some Observations Thereon” Phil. Trans. 18, 183-190, 1694″

Categories
General Observations slow

The coffee cave

Americano, Caravan coffee, Skylark, Wandsworth
Gazing into a coffee you can see the reflection of your face looming back at you.

Have you ever gazed into your coffee as you take a mouthful only to get disturbed to see a distorted view of your face looming back at you from the coffee? Has it struck you that while you often see such reflections, you rarely see shadows? Try it first with water and then coffee. Can you, perhaps, see a shadow on the coffee where you cannot see shadows on the water? Why would this be?

For a shadow to be visible on a surface, the surface must scatter enough light so that the contrast between shadow (where there is no light to scatter) and non-shadow (where the surface is illuminated) can be seen. Although a shadow (or at least the relative lack of light) is always going to be present behind any obstacle, it is whether or not it can be seen on the surface of the water/coffee that is at issue here. Pure water is of course quite transparent. Without anything in the water to scatter the light (such as mud for example), the light passes straight through the water to the other side. Overall, not enough light is scattered back from the surface of the water to generate the contrast required for seeing shadows. Seeing shadows on pure water is going to be hard.

Chemex, 30g, coffee
The concentration of suspended particles will depend on how you make your brew

By contrast, coffee contains suspended particles, in fact they are part of the very essence of the drink. These particles offer a surface to scatter the light back towards the observer and so highlight the shadows formed by the object between the coffee and the light. It strikes me that different brew methods will result in different amounts of sediment and suspended particles in the coffee and therefore a greater or lesser tendency of the coffee to reveal shadows. Perhaps if anyone does notice that it is harder to form shadows on coffee prepared by a Chemex  than a French Press (for example) they could let me know using the comments section below.

Shadows have been used by philosophers to illustrate by allegory how we perceive the world around us. In the tale of Plato’s cave a group of prisoners are held in a cave such that they can only ever see the shadows playing on the cave’s wall. The shadows are formed by a fire behind the prisoners that the prisoners cannot see. As they can only see the shadows, they start to think that it is the shadows themselves that are ‘real’. It is a tale questioning the reality of what we currently see and also our inability to adjust to the differences between looking directly at the Sun or discerning shadows in the dark. In the story of the cave, it is the fire, or the Sun that causes the shadows that deceive the prisoners. No consideration was given to the role played by the wall on which the shadows dance. Yet we can see from our coffee that to understand the world of shadows we do not merely need a light source. To understand shadows, we need a surface from which to reflect the shadows. Perhaps we need to spend some time contemplating our coffee, the shadows and what they can tell us about the world and how we see it.

For details about this and other phenomena involving light and its interaction with the world around us, see: “Color and Light in Nature”, David K. Lynch and William Livingston

 

Categories
Coffee review Observations Science history slow

Bridging worlds at White Mulberries, St Katherine’s Docks

chalkboard at White Mulberries
Sign board at White Mulberries.

Five minutes walk from the Tower of London is an area that feels far removed, physically and metaphorically, from the crowds swarming around the central tourist sights. St Katherine’s Docks offer a peaceful retreat a stone’s throw away from the bustle of the Tower. And if you are in this area, there is no better place to have a coffee (and potentially a cake) than White Mulberries. This café looks over the central basin of the three docks in St Katherine’s and is, seemingly, in the only 19th century warehouse still standing in the docks. On each occasion I have visited White Mulberries the coffee has been very good. As a black coffee drinker, the taste of the coffee has to be great as there is no hiding a bitter espresso with the milk of a latte and White Mulberries has passed every time (their website says that they rotate the coffee roasters, so I can only assume that they have a great relationship with their suppliers). If Latte Art is your thing though, White Mulberries also has that. It was an example of the latte art at White Mulberries that accompanied my recent article in Physics World.

Bascule Bridge, St Katherine's Docks
A moving bridge at the entrance to St Katherine’s Docks. There are youtube videos of this opening.

The point of a “café-physics” review on Bean Thinking though is only partly about the great coffee on offer (all cafes that are featured in the Daily Grind have great coffee). Part of the point of a café-physics review is to look around, slow down and notice things and see what physics there is around the café in question. There is always something to notice, always something science-like to appreciate. White Mulberries is no different, with an enormous number of things to notice, from the water in the docks to the Aeolian harps made by the rigging on the yachts moored nearby. What I would like to concentrate on today though are the bridges. Bridges are often used in scientific outreach with children. I think it is partly because so many concepts in physics can be communicated by practising making bridges. Forces need to be balanced (Newton), stress and strain needs to be considered, the properties of materials are unconsciously learned. And this, I think is another reason that bridges are a great ‘outreach’ tool, because bridges are inherently multidisciplinary. To make a good bridge requires elements from physics, chemistry, mechanical and civil engineering and art to name just a few. A bridge needs to satisfy the aesthetic demands of the public that use it as well as the structural demands of the people that will stand on it. And the bridges in the docks required yet more work and more understanding, for these aren’t just bridges that span a waterway, these bridges need to move somehow to allow boats to pass, either by having a platform that rises up (as with the nearby Tower Bridge), or platforms that swing around (which was the design of some of the original bridges at St Katherine’s Docks). Great thought and understanding went into the design and building of these mechanisms for moving the bridges. There is much to be gained by contemplating bridge design.

Microcord image of Tower Bridge with tourist in foreground
Tower Bridge, Photo © Artemisworks Photography, http://www.artemisworks.plus.com

Which brings us to another bridge, this time a metaphorical one between White Mulberries and the Coffee Houses of the past. The designer of St Katherine’s Docks was Thomas Telford (1757-1834). As well as specifying the design of the docks, he was responsible for some of the original bridges in the docks themselves, particularly a swing bridge that was built in 1828. St Katherine’s Docks was Telford’s only London project but that didn’t stop him from being a regular in a Coffee House near (what is now) Trafalgar Square. For many years Telford drank coffee in the Salopian Coffee House (most likely in Spring Gardens, just behind Cockspur St). This was where he stayed when in London and, as he was a famous engineer by that point, he started to attract crowds of engineers and admirers to the Salopian in the hope of meeting him. So important was Telford to the business of this central London coffee house that, when he left to live in Abingdon St, the new landlord of the Salopian complained to him “What, leave the house? Why sir, I have just paid £750 for you!”.

Fortunately, White Mulberries has far more to attract customers to it than one illustrious coffee drinker, though perhaps it has those as well.

 

White Mulberries is at St Katherine’s Docks, E1W 1AT,

A good book on bridges is: “Bridges – the science and art of the world’s most inspiring structures”, David Blockley, Oxford University Press (2010)

Coffee House anecdotes from “London Coffee Houses”, Bryant Lillywhite (1963)

Categories
slow

The importance of going slow

journals in a library
How can we assess the work of scientists? Should we count the number of papers that they write?

In the past few weeks there has been a bit of a media storm about the state of science. A paper that had been published in the journal Science, was retracted because it turned out that the study had, quite possibly, been faked. The retraction highlighted the problem of “publish or perish” which has been a concern for many scientists of late. A second article, this time an editorial in Nature, took a different and perhaps surprising perspective on things. Apparently the public trust scientists much more than scientists think that they do. Why would that be the case?

These two stories should concern us because they lie at the heart of a current problem in science. According to the dictionary, ‘science’ is “systematic and formulated knowledge”. Such knowledge takes time to develop, it takes us time to understand what goes on, both on an individual level and as a society. The ‘publish or perish’ culture acts in opposition to this. Within a ‘publish or perish’ culture, the way that science works is that the more papers that you have, especially those that get cited and are published in (apparently) good journals, the more successful you will be in your career and in your ability to get research funding. It is essential to publish “high impact” papers in order merely to survive in science. In more extreme cases this has led to data being faked and subsequent retractions of the papers (if it is ever discovered). Active faking of data though is only the tip of the iceberg. The pressure to publish high profile papers quickly, can lead to the original paper not having been investigated thoroughly enough. In fact, there are even motivations to publish too quickly. Firstly, if you are wrong, you just publish a second paper a few months later. Two papers, two sets of citations. Secondly, publishing early means getting there first, ie. more citations. It has got to the point where it is advantageous to quickly publish poor quality research with hyped key words than it is to do a thorough job and perhaps be beaten to the publication by a more incomplete work. This cannot be good for science or our society and it suggests that, in order to have a scientific career you must, to a greater or lesser extent, cease to behave scientifically. It is perhaps for this reason that scientists themselves have a doubt as to why the public would trust them, they no longer trust themselves.

lilies on water
Is there symbolism here? There’s certainly a lot of physics.

The ‘publish or perish’ culture has come about partly as a consequence of needing a metric by which to judge the worth of research. In itself this is understandable but it does suggest that we are no longer confident of our ability, as a society, to measure the ‘good’ of something. To judge something as ‘good for society’ necessarily involves many different inputs from many disciplines. Assessing something as good is a value judgement. To redefine ‘good’ purely into something that we measure (by profit, or by number of papers) is to artificially reduce what is good for society to an arbitrary, but on appearance scientific, method. Rather than admit that questions over what is ‘good science’ are, essentially, value judgements, we try to give a false ‘scientific’ measure of their worth, one based on citations and publications. We still have our biases but we have become less conscious of them and instead try to hide them with a false scientism.

How could we change this, how else can we assess who is a ‘good’ scientist or what research will benefit society? This is, I think where it is important for everyone to get involved and to slow down. It is open for everyone to investigate, for themselves, what they think would make a ‘good’ society. Clearly the quest for knowledge, and in particular scientific knowledge, will form part of that good but for us, as a society to realise what is good we need to stop and think about it. There is a need to encourage clear methods of thinking but at the same time everyone must feel eligible to be a part of this natural philosophy, purely as a consequence of their being a citizen of society. On a practical level, this can be achieved by our maintaining a sense of awe and wonder at the beauty of the world, and society, around us. In my own field of magnetism for example, to know the physics behind magnetic attraction is to make it more beautiful. And that is in essence what I am trying to communicate with Bean Thinking; just as an artist does with a painting, I am attempting to share the beauty that I see as a result of seeing physics all around me. The saying of Pierre Duhem that “Physical theory is a mathematical painting of reality” can be taken at many levels. As a scientist, I am to a certain extent, an artist.

rain drops on a tulip
A tulip in spring. The water droplets on the petals suggest some very deep physics. As the flower opens into the sunshine, each layer  (physical and metaphorical) of petals reveals a new level of beauty.

Of course, there is no immediate connection between appreciating the beauty of knowledge and allocating research funds. Yet if we, as a society, appreciate science and beauty where we see it, we are going to slowly move back to a more sustainable, scientific way of doing science. “By learning to see and appreciate beauty, we learn to reject self-interested pragmatism”¹. By allowing ourselves to assess the good of society across many measures, we recover science. Denying the fact that what qualifies as ‘good’ is ultimately a value judgement and instead covering it in false metrics, imperils science. It is in the history of humanity to ask ‘why’. Moving to a predominantly technology driven quasi-science does not enrich us as a species. Good art, good music, great science can. Great discoveries of the past have not been obtained by chasing the latest chimera of a device, they have been uncovered through an insatiable curiosity. A demand to know ‘why’ things are the way they are. We are destroying the very science we are so keen to promote if we conform to the key-word, hype and technology driven ‘publish or perish’ culture. It has got to the point where, in order to save science, it is imperative that we, as a society, recover our ability to appreciate the beauty in science.

I hope that Bean Thinking prompts at least some people to question the world around them. It is not important to agree with what is written in Bean Thinking indeed, perhaps with some things it is more important to disagree. The key thing is to notice the world around. The practise of slowing down and noticing things is the reasoning behind the cafe-physics reviews, as much as anything it enables me to practise slowing down and noticing too. To slow down and to appreciate what is there will mean that slowly, imperceptibly perhaps, we challenge the culture of ‘publish or perish’. To do so may not be too far short of a need to recover our humanity, to quote Laudato Si’ again, “[w]e need to see that what is at stake is our own dignity”².

¹ Pope Francis, Laudato Si’, (2015) #215

² ibid, #160

Further thoughts:

Michael Polanyi “Science, Faith and Society”, Sapientia Press, 1964

Michael Polanyi “Personal Knowledge: Towards a post-critical philosophy”, University of Chicago Press, 1974

Categories
Coffee cup science General Observations slow

Coffee & Contrails (II)

vortices in coffee
Vortices forming behind a tea spoon being dragged through coffee.

Drag a tea spoon through your cup of coffee (or tea). Start by dragging the spoon slowly, then faster. Initially, the coffee flows around the spoon smoothly then, as you speed up, small vortices appear at either side of the spoon. Pull the spoon out of the coffee, and the vortices continue to move together through the cup before bouncing off the sides. Such vortices form whenever there is a speed difference between two layers of fluid (gas or liquid), as there is around the spoon being dragged through coffee. It is this effect that is the second connection between the physics of coffee and contrails.

Of course it is not giant tea spoons in the air but aeroplanes. Behind each aeroplane is a series of vortices trailing behind the wings. These vortices do not (normally) cause the contrails, the reason that they form was discussed in Coffee & Contrails (I). However, the vortices do cause some interesting effects in the contrail that we can, occasionally, see.

wake vortex, contrail, coffee in the sky
In this contrail there is a set of protuberances at regular intervals along the lower edge.

As the plane moves through the air, the speed of the air going over the wing is greater than the speed of air under the wing. As well as leading to vortices forming behind the wing, this speed difference results in an air pressure difference (the air pressure under the wing is greater than the air pressure above the wing). The pressure difference (below and above the wing) pushes the plane upwards, or, perhaps more technically, ‘creates lift’ and enables the plane to fly. If you want a good demonstration of the fact that a higher air speed leads to a lower air pressure, get two pieces of flat A4 paper and hold them in front of you such that you are looking through the small gap between them. Now blow into the gap separating the two sheets; they will join together. The reason that they do this is that the air pressure for fast moving air (as you blow) is less than the air pressure for static air (around the paper) and so the difference in air pressure pushes the two sheets together.

Shadowy contrail
Look carefully for another interesting contrail optical effect. There are two contrails here, an obvious one cutting straight down the photo and a second contrail moving more horizontally across the photograph. The second contrail can be seen more clearly by its shadow.

On a clear day, if the air in the higher atmosphere is relatively humid, you will see lots of persistent contrails. These contrails last for a long time in the skies and can drift with the wind. Occasionally at the edge of such a contrail you will see regular protrusions from the contrail, almost as if waves are forming on the contrail and producing white horses in the sky (see picture above). Initially I had hoped that this was a manifestation of the Kelvin-Helmholtz instability however the actual explanation is still quite fascinating. It seems that these protrusions are the result of the “wake vortices“, the vortices that form behind a plane just as the coffee forms vortices behind your spoon. I find it quite impressive to realise that high in the sky, these contrails are showing us that the atmosphere behaves just as if it were a cup of coffee. A definite case for which a coffee is a telescope for viewing the world.

Please leave any comments in the comments box below. If you think of any other connections between the physics of coffee and contrails please share them either here or on my Facebook page.